There is known an ignition coil for an internal combustion engine that has a coil body formed by accommodating a primary coil and a secondary coil within an insulating body case, and a high-voltage tower formed by disposing a high-voltage output terminal that is electrically connected to the secondary coil as well as projecting from the coil body towards a tip side thereof inside the high-voltage tower.
An ignition coil that has a resistive element inserted and disposed in a space at a tip side of the high-voltage output terminal in the high-voltage tower is disclosed in the Japanese Patent Application Laid-Open Publication No. 2011-35019.
As the resistive element, a wire-wound resistor can be used.
The wire-wound resistor has an insulating core material, a conductor winding wound spirally on an outer periphery of the core material, and metal caps disposed at both ends of the core material in an axial direction.
However, the following problems may occur in the ignition coil with the wire-wound resistor as described above.
That is, in the wire-wound resistor, the metal caps are required to be disposed at both ends of the core material in the axial direction as conduction terminals so as to contact the conductor windings from an outer peripheral side thereof.
Further, in order to prevent the conductor windings from becoming displaced in the axial direction relative to the core material, resin is required to be filled between parts of the conductor windings that are adjacent in the axial direction in an outer peripheral surface of the core material.
Here, the conductor windings are required to be exposed from the resin at the outer periphery thereof so that the conductor windings and the metal caps can be contacted.
However, since it is difficult to dispose the resin reliably between the parts of the conductor windings that are adjacent in the axial direction while exposing the entire outer peripheral surface of the conductor windings, in practice, a state is likely to occur where the parts of the outer peripheral surface in the conductor windings that are exposed and the parts that do not are not exposed coexist.
In such a state, creeping discharge may occur to the exposed conductor windings from the metal caps via a surface of the resin.
If creeping discharge occurs, this creeping discharge may become electromagnetic noise and is likely to affect peripheral devices.
Moreover, in the long term, there is also a concern the breakage of the conductor winding may occur due to the creeping discharge due to a deterioration of the resin between the conductive windings.
Here, it is conceivable to prevent the creeping discharge and damage of the conductor windings from occurring by preventing the exposure of the conductor windings by covering the entire conductor windings from the outer periphery thereof by the resin.
However, in this case, a problem that electrical conduction between the conductor windings and the metal caps become difficult may occur.